1. Field of Invention
The present invention is to provide a kind of liquid crystal aligning film composition used for LCD, in which the liquid crystal aligning film composition used for LCD is a containing cholesterol structure of polyimide resin oligomer (A) mixed with the second reagent (B), through an induced process (C), to produce a thin film for aligning liquid crystal molecule.
2. Description of the Prior Art
LCD plays an extremely important role in the electroptical industry; especially, it was developing very quickly in recent years. According to the application of electrical devices is widely developed, demands of LCD are also increasing fast, small size panel such as a personal celluar telephone and a personal digital assistant (PDA), large size panel such as a notebook computer and liquid crystal monitor (LCD monitor), and the like. In recent years, due to the promotion of manufacturing technique and the participation of related material industry the application of LCD is developing to the more advanced level, and the prospect is very positive.
At present, the aligning method most widely used in LCD industry is to rub the coated aligning film substrate plate toward to one direction with a mechanical force, and liquid crystal molecule can be generated the uniform and stable aligning effect, said as rubbing treatment. The advantages of this method are effective mass production as well as stable aligning effect. However, at present, since the aligning polymer film has no sufficient toughness, after rubbing, it is easily separated from the substrate plate or causes crack. After assembling to LCD, this kind xe2x80x9cinjuredxe2x80x9d aligning film can absorb ionic charge with giving voltage; and after relieving voltage, the residue voltage can be accumulated. Residue voltage causes to the image sticking effect in the picture and contrast decreasing. In addition, since the aligning film is not capable of rubbing resist, it produces a lot of tiny particles and dust, and it causes to the partial discharge effect during giving voltage, and it would hurt the aligning film itself and indium tin oxide (ITO) electrode or thin film transistor (TFT). Also, the formation of defects on the surface of aligning film would cause phase distortion and light scattering to lower down the display quality.
Especially, in the super twisted nematic liquid crystal display (STN-LCD) manufacturing process it needs much stronger rubbing treatment and larger allowed margin, therefore, the rubbing resistibility for aligning film is more critical.
In general, LCD aligning agent is almost made of polyimide material, which is obtained from dianhydride and diamine via polymerization addition, and the components what they are used are in accordance with the characteristics of obtained polyimide products.
U.S. Pat. No. 5,698,135 discloses a kind of improved rubbing resistibility of aligning film by using several aliphatic dianhydrides. However, the claimed aliphatic anhydride has no good reactivity to cause the synthetic reaction be difficult.
Japan Patent 9-185065 discloses a kind of increasing rubbing resistibility of aligning film by using thermal crosslinking compound, however, the residue voltage is still too high, and it is unsuitable for high grade LCD.
It desires to reach much better requirements of electrical property for aligning film such as high voltage holding ratio (VHR), low charge-accumulation by a direct current voltage, and the like. It refers to Japan Patent 64-4720, Japan Patent 10-183118, U.S. Pat. Nos. 5,858,274 and 5,954,999, which disclose the method, e.g. mixing a polyamic acid resin and a solvent-solube polyimide resin solution with an appropriate ratio, according to the characteristic of material itself polyamic acid possesses low direct current residue voltage, rubbing resistance,low image sticking, and good printing properties; and a solvent-soluble polyimide possesses the advantages of high voltage holding and low baking temperature, after mixing, it would to promote the electrical properties; however, since the portion of a solvent-soluble polyimide is less rubbing resistance, therefore, it still has serious problems of powder dust and film stripped off etc. In addition, U.S. Pat. No. 5,954,999 discloses a kind of controlling pretilt angle method, in which a long-chain alkyl group is subjected to a solvent-soluble polyimide, the drawback of this method is that since a long-chain alkyl group is not able to give steric hindrance effectively to cause the problems, e.g. the long-chain itself easily rotates, the pretilt angle is unstable, and aligning uniform decreases. Also, the difficulty control the pretilt angle of LC cell is very worried about to.
Hence, the primary object of the present invention is to solve the drawbacks described above. In order to avoid the presence of the drawbacks described above, the present invention is to provide a kind of liquid crystal aligning film composition used for LCD, which is not easily to cause the rubbing injure and powder dust. The other object of the present invention is to provide a kind of liquid crystal aligning film composition used for LCD, which can keep high voltage holding ratio and low charge-accumulation by a direct current voltage.
The other object of the present invention is to provide a kind of liquid crystal aligning film composition used for LCD, which is no image sticking.
The other object of the present invention is to provide a kind of liquid crystal aligning film composition used for LCD, which can fit to the high and/or low pretilt angle for various display application.
The other object of the present invention is to provide a kind of liquid crystal aligning film composition used for LCD, which is easy for the synthetic reaction process.
In order to reach the objects described above, the present invention is referred to that a containing cholesterol structure polyimide resin oligomer (A) and the second reagent (B) are mixed together, through an induced process (C), to produce a thin film for aligning liquid crystal molecule, which can be easily synthesized, has high rubbing resistance, and can fit to the high and/or low pretilt angle for various display application.